The extended structure of the dwarf irregular galaxy Sagittarius
Abstract
We present a detailed study of the stellar and H i structure of the dwarf irregular galaxy Sagittarius. We use new deep and wide field photometry to trace the surface brightness profile of the galaxy out to ≃5.0' (corresponding to ≃1600 pc) and down to μV ≃ 30.0 mag/arcsec2, thus showing that the stellar body of the galaxy is much more extended than previously believed, and it is similarly (or more) extended than the overall H i distribution. The whole major-axis profile is consistent with a pure exponential, with a scale radius of ≃340 pc. The surface density maps reveal that the distribution of old and intermediate-age stars is smooth and remarkably flattened out to its edges, while the associated H i has a much rounder shape, is off-centred and presents multiple density maxima and a significant hole. No clear sign of systemic rotation is detectable in the complex H i velocity field. No metallicity gradient is detected in the old and intermediate age population of the galaxy, and we confirm that this population has a much more extended distribution than young stars (age ≲ 1 Gyr).
Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under the Program 089.D-0052(A).Table of stellar photometry (IN6) is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/570/A78- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 2014
- DOI:
- 10.1051/0004-6361/201424411
- arXiv:
- arXiv:1409.0715
- Bibcode:
- 2014A&A...570A..78B
- Keywords:
-
- galaxies: dwarf;
- Local Group;
- galaxies: ISM;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 11 pages, 14 figures, accepted for publication on A&